This invention relates to membrane tanks containing cryogenic liquids.
In the storage of very cold liquids in large containers, difficulties arise where stresses are set up in the metal membrane which exceed the elastic limit of the metal. This can cause permanent deformation of the metal membrane and possibly rupture of the metal membrane itself.
To avoid the severe stresses, it is possible to use metal membranes containing corrugations, dimples or wrinkles. One such technique is disclosed in U.S. Pat. No. 3,150,795 entitled "Membrane Tanks". While the membrane tank described in that patent has been found to be a significant advance in the state of the art, it has certain limitations because the dimples allow limited expansion along one axis while restricting expansion along the other axis.
Another technique is disclosed in U.S. Pat. No. 3,184,094 entitled "Extensible Metal Sheets". While this expandable membrane has been found to be a significant advance in the state of the art since it can expand along two axes, it still has certain limitations which are overcome by the present invention. Specifically, due to its complex shape it is hard to manufacture and is susceptible to rupture or permanent deformation where the corrugations intercept.
Other arrangements of corrugations have been proposed. Examples are described in U.S. Pat. Nos. 3,224,621; 3,302,358; 3,215,301; 3,332,386 and 3,547,302. These systems are hard to manufacture because of their complex shape, because metal must expand along two axes where the corrugations meet. Moreover, these systems are susceptible to rupture or permanent deformation where the corrugations intercept.
In contrast, the expandable membrane system of the invention provides that the membrane has to expand only in one axis at the junction of two expansion joints and in expansion joints at right angle to each other. It also provides that adjacent panels assist in the expansion and contraction by rotating in opposite directions.